att.duration provides attributes for normalization of elements that contain datable events.
Membersatt.timed [annotationBlock binaryObject ellipsis gap media] date time
Attributesatt.duration.w3c (@dur) att.duration.iso (@dur-iso)

This ‘superclass’ provides attributes that can be used to provide normalized values of temporal information. By default, the attributes from the att.duration.w3c class are provided. If the module for names & dates is loaded, this class also provides attributes from the att.duration.iso class. In general, the possible values of attributes restricted to the W3C datatypes form a subset of those values available via the ISO 8601 standard. However, the greater expressiveness of the ISO datatypes is rarely needed, and there exists much greater software support for the W3C datatypes.